The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An engine combusts an air/fuel mixture to produce drive torque for a vehicle. Opening of a throttle valve is regulated to control the amount of air drawn into an intake manifold. Air from the intake manifold is drawn into cylinders. A fuel system may inject fuel into the intake manifold or may inject fuel directly into the cylinders.
The byproducts of combustion are exhausted from the vehicle via an exhaust manifold. A high-pressure (HP) turbocharger and a low-pressure (LP) turbocharger are powered by exhaust gases flowing through the exhaust manifold and provide an HP compressed air charge and an LP compressed air charge, respectively, to the intake manifold. A turbine bypass valve (TBV) may allow exhaust gas to bypass the HP turbocharger, thereby reducing the restriction imposed by the HP turbocharger, but increasing the total amount of air charge provided to the intake manifold.
Engine control systems have been developed to control the TBV. Traditional engine control systems, however, do not control the TBV as accurately as desired. For example, an engine control system may determine a position of the TBV using a proportional-integral-derivative (PID) control scheme and a TBV position signal measured by a TBV position sensor. However, variations in the TBV position signal, exhaust pressure, PID control inaccuracies, and/or thermal deformation of the TBV may cause different leaks of the TBV at the closed position. The different leaks result in incorrect calculations and control of exhaust gas that flows through the turbochargers and of the output of the turbochargers, decreasing their efficiency.